The present invention relates generally to inkjet printheads, and more particularly to a wide-array inkjet printhead assembly.
A conventional inkjet printing system includes a printhead and an ink supply which supplies liquid ink to the printhead. The printhead ejects ink drops through a plurality of orifices or nozzles and toward a print medium, such as a sheet of paper, so as to print onto the print medium. Typically, the orifices are arranged in one or more arrays such that properly sequenced ejection of ink from the orifices causes characters or other images to be printed upon the print medium as the printhead and the print medium are moved relative to each other.
In one arrangement, commonly referred to as a wide-array inkjet printing system, a plurality of individual printheads, also referred to as printhead dies, are mounted on a single substrate. As such, a number of nozzles and, therefore, an overall number of ink drops which can be ejected per second is increased. Since the overall number of drops which can be ejected per second is increased, printing speed can be increased with the wide-array inkjet printing system.
Mounting a plurality of printhead dies on a single substrate, however, requires precise alignment between the printhead dies. FIGS. 1A and 1B illustrate mounting of a plurality of printhead dies 90 on a substrate 92 using conventional mounting methods. In FIG. 1A, for example, the printhead dies are mounted on the substrate with an adhesive 94. As such, the printhead dies are pushed down to achieve a predefined force which results in a predetermined gap between the substrate and the printhead dies. In FIG. 1B, for example, the printhead dies are mounted on the substrate with the adhesive and standoffs 96 which are interposed between the printhead dies and the substrate. As such, the printhead dies are pushed down until they contact the standoffs.
With the conventional mounting methods, however, the printhead dies follow the profile of the substrate. Thus, a variation in planarity of the substrate results in a variation of planarity among the printhead dies and, therefore, misalignment between the printhead dies. The printhead dies, therefore, are not coplanar. Unfortunately, misalignment between the printhead dies can adversely affect performance of the inkjet printing system. A variation of planarity among the printhead dies, for example, can result in ink drop trajectory errors as well as pen-to-paper spacing problems which degrade print quality.
Accordingly, a need exists for precisely mounting and aligning a plurality of printhead dies on a single substrate of a wide-array inkjet printhead assembly such that misalignment between the printhead dies is avoided and coplanarity of the printhead dies is achieved.
One aspect of the present invention provides an inkjet printhead assembly. The inkjet printhead assembly includes a substrate having a non-planar surface, a plurality of adhesive quantities each disposed on the non-planar surface of the substrate, and a plurality of printhead dies each adhered to the non-planar surface of the substrate by one of the adhesive quantities. As such, each of the adhesives quantities have a thickness such that the thickness of at least one of the adhesive quantities varies from the thickness of another of the adhesive quantities to compensate for the non-planar surface of the substrate. Thus, the adhesive quantities support the printhead dies and establish a substantially coplanar relationship among the printhead dies.